Other Links

Watermelon Line May Help Breeders Combat Mildew / February 23, 2006
/ News from the USDA Agricultural Research Service

Plant geneticist
Angela Davis and cooperators have released a new watermelon line that may be
useful for introducing resistance to race 1 powdery mildew. Above, Davis
measures the lycopenesource of watermelon's red colorin puree from
a low-sugar watermelon released a few years ago. Click the image for more
information about it.

Watermelon Line May Help Breeders Combat
Mildew

Agricultural Research Service (ARS) researchers and cooperators are
introducing watermelon stock that may help breeders combat powdery mildew, a
disease that threatens watermelon yields and quality in several states.

Recently, two races of powdery mildew have been reported on
watermelon, and they appear to be geographically separate. Existing watermelon
lines, which were thought resistant, were found to be susceptible. But ARS
researchers and colleagues discovered the first documented resistance to race 1
powdery mildew in an ARS germplasm collection.

The scientists first analyzed existing lines from the ARS Southern
Regional Plant Introduction Station in
Griffin,
Ga., for resistance to race 1 using field and growth chamber studies. They
developed the new watermelon line, PI 525088-PMR, by repeatedly selecting the
most resistant plants from the line PI 525088 (Citrullus lanatus var.
lanatus).

According to
Angela
R. Davis, geneticist at the ARS
South
Central Agricultural Research Laboratory in Lane, Okla., watermelon has
historically been resistant to powdery mildew, but the disease has become
widespread during the past few years. A significant problem in Europe and
Africa for about a decade, powdery mildew has emerged as a severe problem in
some areas of the United States.

Powdery mildew appears as a dusty white or gray coating over leaf
surfaces or other plant parts, and can be difficult to control.

The new watermelon line may be useful for introducing resistance to
race 1 powdery mildew (caused by the fungus Podosphaera xanthii,
previously known as Sphaerotheca fulginea auct. p.p.) into
commercial watermelon cultivars. Ultimately, it may also reduce the amount of
fungicide needed to control the disease.